Device and method for tightening a nut placed on a threaded end, and assembled washer and nut for such a device

ABSTRACT

Device ( 10, 20, 30 ) and method for tightening a bolt ( 2 ) or a nut ( 12 ) threaded on its end, which end extends through at least a first body ( 3 ) and screws into a hole ( 5 ) in a second body ( 4 ) or extends through the second body into another nut ( 13 ). The device has gripping means ( 7, 17 ) co-acting with the bolt-head or the nuts. Means ( 8 ) process a signal generated by sensor means ( 18 ) subject to the axial force exerted on the surface of the first body by the bolt-head or the first nut, or on the surface of the second body by the second nut, and control the device such that the bolt-head or a nut is tightened subject to the axial force exerted on the surface of one of the bodies, which sensor means are in an annular body ( 16 ) around the threaded hole between the bolt-head or first nut and the first body or between the second nut and second body.

The invention relates to a device for tightening a bolt head withthreaded end or a first nut placed on a threaded end, which threaded endextends through a hole in at least a first fixed body and is screwedinto a threaded hole in a second fixed body, or extends through a holein a second fixed body and is screwed into a second nut, which device isprovided with gripping means co-acting with the bolt head or the firstor the second nut.

It is known to secure a nut on a threaded end using for instance ahydraulically, pneumatically or electrically driven torque wrench. Arotatable socket, the internal dimensions of which correspond to theexternal dimensions of the nut, is herein placed over the nut and setinto rotation until a predetermined value of the torque exerted on thenut is reached and the rotation stops.

The known torque wrench has the drawback that the value of the forceexerted on the surface of the first or second fixed body by the nut inaxial direction of the threaded end has a great distribution, even ifthe torque is adjusted very precisely. A cause of this is that the axialforce resulting at a determined adjusted torque depends on, among otherfactors, the friction force which occurs between the screw thread flankof the nut and the threaded end and between the support surface of thenut and the surface with which this nut is in contact. These frictionforces are determined by, among other factors, the type of lubricationapplied, the tolerances in the dimensioning of the co-acting screwthreads, the shearing and bending forces which occur, the degree ofparallelism of the co-acting contact surfaces, the composition of theapplied materials and the condition of the surfaces in question. It isknown that the force exerted in axial direction by different nuts, whichare secured to the surface of a first flange at the same set value forthe torque exerted using a torque wrench, in order to couple this firstflange to a second flange can differ by up to about 40%. Suchdifferences are undesirable with a view to the reliability and thedurability of the intended coupling of the flanges.

It is further known to secure a nut on a threaded end using for instancea hydraulic jack system. The jack system is herein used to pull on thethreaded end until a predetermined value of the exerted tensile force isreached, after which the nut is tightened manually or mechanically ontothe surface of the body for securing and the tensile force exerted bythe jack system is then reduced to zero. It is known that the maximumexerted tensile force is here not transferred integrally to the threadedend locked by the tightened nut. The extent to which the tensile forceis transferred is determined by, among other factors, the ratio betweenlength and diameter of the threaded end, the extent to which thethreaded end is perpendicular to the surface of the first fixed body,the operating method of an operative, the possibly applied gaskets,friction occurring between the co-acting screw threads and roughness andcontamination of the contact surfaces in question. It is known that inorder to couple this first flange to a second flange the force exertedin axial direction by different nuts secured on the surface of a firstflange at the same set axial bias can differ by up to about 50%. Suchdifferences are undesirable with a view to the reliability and thedurability of the intended coupling of the flanges.

It is an object of the invention to provide a device whereby a bolt headwith threaded end or a nut placed on a threaded end can be tightenedwith great precision with a preset value of the force exerted by thisbolt head or nut in axial direction of the threaded end.

It is a further object to provide such a device which is suitable forapplication with different types of bolt and nut which may or may not beprovided with a standard washer.

It must be possible to supply the power required for this device in anyusual form, for instance hydraulic, pneumatic or electrical.

These objectives are achieved, and other advantages gained, with adevice of the type stated in the preamble, wherein according to theinvention processing and control means are provided for processing asignal generated by sensor means subject to the force exerted in axialdirection of the threaded end on the surface of the first fixed body bythe bolt head or the first nut, or on the surface of the second fixedbody by the second nut, and for controlling the device in a manner suchthat the bolt head, the first or the second nut is tightened subject tothe force exerted in axial direction of the threaded end on the surfaceof the first fixed body by the bolt head or the first nut, or on thesecond fixed body by the second nut, which sensor means are received inan annular body arranged round the threaded end between the bolt head orthe first nut and the first fixed body or between the second nut and thesecond fixed body.

A device according to the invention makes it possible to tighten a boltor nut directly in axial force-controlled manner, this in contrast tothe above described known devices, which operate in torque-controlledmanner or, using a jack, indirectly in axial force-controlled mannerwith intervention by an operator.

The signal generated by the sensor means can be transmitted to theprocessing and control means in per se known manner using a cable.

In a preferred embodiment of a device according to the inventiontransmission means are provided for wireless transmission to theprocessing and control means of the signal generated via the sensormeans.

These transmission means are for instance adapted to send and receive aradiographic signal or a light signal, in particular an infrared signal.

The sensor means are for instance formed by a film of a magneto-elasticmaterial which is received, surrounded by a pick-up coil, in an annularholder as known from European patent publication EP 0 814 328.

In a simple embodiment the sensor means are received in a washer, theinner diameter of which corresponds to the diameter of the threaded end.

In another embodiment the sensor means are received on the peripheralsurface, for instance in a peripheral groove, of a nut or ring, thescrew thread of which co-acts with the screw thread of the threaded end.

In a subsequent embodiment the sensor means are received in an annularpart of an assembled washer which is adapted to tighten a nut to beplaced on this washer.

Such a washer is for instance assembled from a screw thread segment anda ring, wherein the ring is provided with a gripping profilecorresponding to the gripping means and wherein the screw thread segmentis received in the ring with a press fit and is provided with aninternal screw thread co-acting with an external screw thread of thethreaded end.

Using a gripping means suitable for the purpose, such a washer isparticularly suitable, in combination with a normal nut, for the purposeof tightening this nut.

In yet another embodiment the sensor means are received in an annularpart of an assembled nut which is adapted for tightening of this nut inaxial direction of the threaded end in the absence of a torque exertedon the threaded end.

Such an assembled nut is for instance assembled from an outer nut, aninner nut and a washer, wherein the outer nut is provided with agripping profile corresponding to the gripping means and with aninternal screw thread co-acting with an external screw thread of theinner nut, wherein the inner nut is further provided on an outer endwith an internal peripheral profile for inserting therein a lockingelement for the purpose of locking the inner nut against rotation, andon another outer end with an internal screw thread corresponding to thethreaded end and with an external peripheral profile in axial directioncorresponding to an internal axial peripheral profile in the washer. Arotation of the outer nut in the correct direction by means of exertingan external torque, while simultaneously locking the inner nut againstrotation, results in an axial displacement of the inner nut relative tothe washer with simultaneous axial displacement of the threaded endcoupled to the inner nut relative to the washer and the outer nut.

Such an assembled nut is particularly suitable for use in difficultconditions, for instance at high temperatures, extremely high forces ora limited accessibility of the nut.

The invention further relates to a method for simultaneously tighteningat least two bolt heads with threaded end or two first nuts placed on athreaded end, which threaded ends extend through a hole in at least afirst fixed body and are screwed into a threaded hole in a second fixedbody, or extend through a hole in a second fixed body and are screwedinto a respective second nut, which method according to the invention ischaracterized by the simultaneous use of an above described device foreach of the bolt heads or nuts for tightening.

The invention will be elucidated hereinbelow on the basis of exemplaryembodiments, with reference to the drawings.

In the drawings

FIG. 1 shows a greatly simplified schematic representation of a firstembodiment of a device according to the invention in a firstapplication,

FIG. 2 shows a greatly simplified schematic representation of a secondembodiment of a device according to the invention in a secondapplication,

FIG. 3 shows a greatly simplified schematic representation of a thirdembodiment of a device according to the invention in a thirdapplication,

FIG. 4 a shows an axial cross-section and FIG. 4 b a top view of a firstexample of a nut with sensor for use in combination with a deviceaccording to the invention, and

FIG. 5 a shows an axial cross-section and FIG. 5 b a top view of asecond example of a nut with sensor for use in combination with a deviceaccording to the invention, and

FIG. 6 a shows an axial cross-section and FIG. 6 b a top view of anassembled washer with sensor for use in combination with a deviceaccording to the invention, and

FIG. 7 shows an axial cross-section of a first example of an assemblednut with sensor for use in combination with a device according to theinvention.

FIG. 8 a shows an axial cross-section and FIG. 8 b a top view of asecond example of an assembled nut with sensor for use in combinationwith a device according to the invention.

Corresponding components are designated in the figures with the samereference numerals.

FIG. 1 shows a first tool 10 which is applied for tightening a threadedend 1 with fixed bolt head 2 in order to secure a first fixed body 3 toa second fixed body 4, in which a blind threaded hole 5 is formed. Bolthead 2 rests on a washer 6 in which an axial force sensor (not shown) isreceived. Tool 10 is assembled from a drive head 7 provided with arotatable profile (not shown) corresponding to an internal or externalprofile of bolt head 2, and a processing and control unit 8. The sensorin washer 6 is connected via a cable 9 to processing and control unit 8,which is in turn connected to drive head 7 via a cable 11 (or in somecases to an air hose or a hydraulic hose).

FIG. 2 shows a second tool 20 which is applied for tightening a threadedend 1 with a first nut 12 in order to secure a first fixed body 3, forinstance a first flange, to a second fixed body 4, for instance a secondflange, wherein threaded end 1 protrudes through a hole through the twoflanges, and onto the bottom side of which threaded end a second nut 13is screwed. First nut 12 rests on a washer 6 in which an axial forcesensor (not shown) is received. Tool 20 is assembled from a drive head7, provided with a rotatable inner profile (not shown) corresponding tothe outer periphery of first nut 12, and a processing and control unit8. The sensor in washer 6 is connected via an infrared transmitter 14 toa receiver 15 in processing and control unit 8, which is in turnconnected to drive head 7 via a cable 11.

FIG. 3 shows a third tool 30 which is applied for tightening a threadedend 1 with a first nut 12 in order to secure a first fixed body 3, forinstance a first flange, to a second fixed body 4, for instance a secondflange, wherein threaded end 1 protrudes through a hole through the twoflanges and onto the bottom side of which threaded end a second nut 13is screwed. First nut 12 rests on an assembled washer 16 in which anaxial force sensor 18 (shown in FIG. 4 a) is received. Washer 16 isassembled from a screw thread segment (shown in FIG. 6 a) and an innerring, wherein the inner ring is provided with a gripping profilecorresponding to a first inner profile of an auxiliary tool 17, andwherein the screw thread segment is received with a press fit in theinner ring and is provided with an internal screw thread co-acting withan external screw thread of threaded end 1. Auxiliary tool 17 isprovided with a second, rotatable inner profile which corresponds to theouter periphery of first nut 12 and which can be set into rotation by adrive head 7. Tool 30 is assembled from drive head 7, auxiliary tool 17and a processing and control unit 8. The sensor in washer 16 isconnected via an fm radio transmitter 14 to a receiver 15 in processingand control unit 8, which is in turn connected to drive head 7 via acable 11.

FIG. 4 a, b show a nut 37 (FIG. 4 a in a cross-section along line a-a inFIG. 4 b) which can be fixed on a threaded end 1 using a device 10, 20,30 according to the invention, wherein sensor 18 is made up of anannular strip of an elasto-magnetic material around which a pick-up coilis wound, and is received in a peripheral groove 36 in nut 37.

FIG. 5 a, b show an assembled nut 38 (FIG. 5 a in a cross-section alongline a-a in FIG. 5 b) which can be fixed on a threaded end 1 using adevice 10, 20, 30 according to the invention, wherein sensor 18 isreceived in a peripheral channel between component parts 39,40 of nut38.

FIG. 6 a, b show washer 16 of FIG. 3 (FIG. 6 a in a cross-section alongline a-a in FIG. 6 b) with sensor 18, made up of an inner ring 19provided with a gripping profile 21 corresponding to the internalgripping profile of auxiliary tool 17 shown in FIG. 3, and of a screwthread segment 22 which is received with a press fit in inner ring 19and is provided with an internal screw thread 23 co-acting with anexternal screw thread of threaded end 1. Sensor 18 is assembled from anannular strip of an elasto-magnetic material round which a pick-up coilis wound, and is received between inner ring 19 and an outer ring 24fitting closely therearound.

FIG. 7 shows an axial cross-section of an assembled nut 25 which isassembled from of an inner nut 29 and an outer nut 26, provided with acrenellated edge 27 corresponding to the gripping profile of a drivehead, and with an internal screw thread 28 corresponding to an externalscrew thread of inner nut 29, wherein inner nut 29 is also provided onits top side with an internal spline toothing 31 for insertion thereinof a locking element for the purpose of locking inner nut 29 againstrotation, and on its bottom side with an internal screw thread 32corresponding to the threaded end for tightening, and with an externalspline toothing 33 corresponding to an internal spline toothing in awasher made up of parts 34, 35, wherein a sensor 18 is enclosed betweenthe component parts 34, 35. A rotation of outer nut 26 in the correctdirection by means of exerting an external torque while simultaneouslylocking inner nut 29 against rotation results in an axial displacementof inner nut 29 relative to washer 34, 35, with simultaneous axialdisplacement of a threaded end coupled to inner nut 29, wherein theforce exerted in axial direction by washer 34, 35 on the surface of aworkpiece for connecting can be determined very precisely using sensor18 and a processing and control device coupled thereto.

FIG. 8 a, b shows an assembled nut 41 (FIG. 8 a in a cross-section alongline a-a in FIG. 8 b), which is assembled from an outer nut 26, an innernut 29 and a washer 34, 35, wherein outer nut 26 is provided with aspline toothing 27 co-acting with drive head 7 and with an internalscrew thread 28 co-acting with an external screw thread of inner nut 29,wherein washer 34, 35 is provided with an external spline toothing 33for arranging a locking element therearound and with an internal splinetoothing 33 which co-acts with an external spline toothing 33 on a partof the outer periphery of inner nut 29 in order to lock washer 34, 35and the inner nut 29 coupled thereto against rotation. A sensor 18 isenclosed between component parts 34, 35 of washer 34, 35. A rotation ofouter nut 26 in the correct direction by means of exerting an externaltorque, while simultaneously locking inner nut 29 against rotation,results in an axial displacement of inner nut 29 relative to washer 34,35 with simultaneous axial displacement of a threaded end coupled toinner nut 29, wherein the force exerted in axial direction by washer 34,35 on the surface of a workpiece for connecting can be determined veryprecisely using sensor 18 and a processing and control device coupledthereto.

1. Device for tightening a first nut placed on a threaded end, whichthreaded end extends through a hole in at least a first fixed body andis screwed into a threaded hole in a second fixed body, or extendsthrough a hole in a second fixed body and is screwed into a second nut,which device is provided with gripping means co-acting with the first orthe second nut, wherein processing and control means are provided forprocessing a signal generated by sensor means subject to the forceexerted in axial direction of the threaded end on the surface of thefirst fixed body by the bolt head or the first nut, or on the surface ofthe second fixed body by the second nut, and for controlling the devicein a manner such that the first or the second nut is tightened subjectto the force exerted in axial direction of the threaded end on thesurface of the first fixed body by the first nut or on the second fixedbody by the second nut, which sensor means are received in an annularbody arranged around the threaded end between the first nut and thefirst fixed body or between the second nut and the second fixed body,wherein the sensor means are received in an annular part of an assemblednut which is adapted for tightening of this nut in axial direction ofthe threaded end in the absence of a torque exerted on the threaded end.2. Device as claimed in claim 1, wherein transmission means are providedfor wireless transmission to the processing and control means of thesignal generated by the sensor means.
 3. Device as claimed in claim 1wherein the transmission means are adapted to send and receive anoptical or an electrical signal.
 4. Device as claimed in claim 1 whereinthe sensor means are received in a washer, the inner diameter of whichcorresponds to the diameter of the threaded end.
 5. Nut to be fixed ontoa threaded end using a device for tightening a bolt head with threadedend or a first nut placed on a threaded end, which threaded end extendsthrough a hole in at least a first fixed body and is screwed into athreaded hole in a second fixed body, or extends through a hole in asecond fixed body and is screwed into a second nut, which device isprovided with gripping means co-acting with the bolt head or the firstor the second nut, wherein processing and control means are provided forprocessing a signal generated by sensor means subject to the forceexerted in axial direction of the threaded end on the surface of thefirst fixed body by the bolt head or the first nut, or on the surface ofthe second fixed body by the second nut, and for controlling the devicein a manner such that the bolt head, the first or the second nut istightened subject to the force exerted in axial direction of thethreaded end on the surface of the first fixed body by the bolt head orthe first nut, or on the second fixed body by the second nut, whichsensor means are received in an annular body arranged round the threadedend between the bolt head or the first nut and the first fixed body orbetween the second nut and the second fixed body, wherein the sensormeans are arranged on the peripheral surface of the nut.
 6. Assemblednut to be fixed onto a threaded end using a device for tightening a bolthead with threaded end or a first nut placed on a threaded end, whichthreaded end extends through a hole in at least a first fixed body andis screwed into a threaded hole in a second fixed body, or extendsthrough a hole in a second fixed body and is screwed into a second nut,which device is provided with gripping means co-acting with the bolthead or the first or the second nut, wherein processing and controlmeans are provided for processing a signal generated by sensor meanssubject to the force exerted in axial direction of the threaded end onthe surface of the first fixed body by the bolt head or the first nut,or on the surface of the second fixed body by the second nut, and forcontrolling the device in a manner such that the bolt head, the first orthe second nut is tightened subject to the force exerted in axialdirection of the threaded end on the surface of the first fixed body bythe bolt head or the first nut, or on the second fixed body by thesecond nut, which sensor means are received in an annular body arrangedround the threaded end between the bolt head or the first nut and thefirst fixed body or between the second nut and the second fixed body,wherein the sensor means are received between the component parts of thenut.
 7. Assembled washer which is adapted to tighten onto a threaded endin axial direction of the threaded end a nut to be placed on this washerin the absence of a torque exerted on the threaded end, provided withsensor means for use in combination with a device for tightening a bolthead with threaded end or a first nut placed on a threaded end, whichthreaded end extends through a hole in at least a first fixed body andis screwed into a threaded hole in a second fixed body, or extendsthrough a hole in a second fixed body and is screwed into a second nut,which device is provided with gripping means co-acting with the bolthead or the first or the second nut, in which device processing andcontrol means are provided for processing a signal generated by sensormeans subject to the force exerted in axial direction of the threadedend on the surface of the first fixed body by the bolt head or the firstnut, or on the surface of the second fixed body by the second nut, andfor controlling the device in a manner such that the bolt head, thefirst or the second nut is tightened subject to the force exerted inaxial direction of the threaded end on the surface of the first fixedbody by the bolt head or the first nut, or on the second fixed body bythe second nut, which sensor means are received in an annular bodyarranged round the threaded end between the bolt head or the first nutand the first fixed body or between the second nut and the second fixedbody, in which device the sensor means are received in an annular partof an assembled washer which is adapted to tighten a nut to be placed onthis washer, wherein it is assembled from a screw thread segment and aninner ring provided with a gripping profile corresponding to thegripping means, which screw thread segment is received in the inner ringwith a press fit and is provided with an internal screw thread co-actingwith an external screw thread of the threaded end.
 8. Assembled nutwhich is adapted for tightening of this nut onto a threaded end in axialdirection of the threaded end in the absence of a torque exerted on thethreaded end, provided with sensor means for use in combination with adevice as claimed in claim
 1. 9. Nut as claimed in claim 8, wherein itis assembled from an outer nut, an inner nut and a washer, wherein theouter nut is provided with a gripping profile co-acting with thegripping means and with an internal screw thread co-acting with anexternal screw thread of the inner nut, wherein the inner nut isprovided on an outer end with an internal peripheral profile forinsertion therein of a locking element for the purpose of locking theinner nut against rotation, and on another outer end with an internalscrew thread corresponding to the threaded end and with an externalperipheral profile in axial direction which co-acts with an internalaxial peripheral profile in the washer.
 10. Nut as claimed in claim 8,wherein it is assembled from an outer nut, an inner nut and a washer,wherein the outer nut is provided with a gripping profile co-acting withthe gripping means and with an internal screw thread co-acting with anexternal screw thread of the inner nut, wherein the washer is providedwith an external peripheral profile in axial direction for arrangingtherearound of a locking element for the purpose of locking the washingagainst rotation, and with an internal peripheral profile in axialdirection which co-acts with an external axial peripheral profile on apart of the outer periphery of the inner ring.